From the Dillon 650 instruction manual.
Decap pin not decaping.
1. Sizing die not screwed down far enough.
2. Decapping assembly not screwed down all the way.
3. Decapping pin bent, broken or missing.
4. Point of decap pin is squared off not rounded (pin gets stuck in anvil and pulls primer back into primer pocket).
5. Berdan primed brass.
a. Berdan primed brass has two flash holes and should not be reloaded.
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